The party was rather large, as it included one other family, a proper unobjectionable country family, whom the Coles had the advantage of naming among their acquaintance, and the male part of Mr. Cox's family, the lawyer of Highbury. The less worthy females were to come in the evening, with Miss Bates, Miss Fairfax, and Miss Smith; but already, at dinner, they were too numerous for any subject of conversation to be general; and while politics and Mr. Elton were talked over, Emma could fairly surrender all her attention to the pleasantness of her neighbour. (Chapter 26)

I wondered about this too. You might be right and it is a parallel to Mr. Elton, it would make sense as you describe it and very funny too. (;D) However I can think of another reason—of course it may mean nothing. I am only speculating. Perhaps the reason the ladies did not come for dinner is because it was a rather large party including Emma, the Westons, Frank Churchill, Mr. Knightley, a proper unobjectionable country family of unknown number, the male part of Mr. Cox’s family which I think is at least a father and a son who was mentioned in Chapter 16. Mrs. Cole is a friend of Miss Bates and visits her in Chapter 19—I think it is strange that she would then think of her as unworthy and slight her on purpose. It also does not seem Mrs. Bates, Jane or Harriet is offended. However, I could be wrong. Is it Emma or the narrator who describes the ladies as unworthy? (;D)